Thermal Stability Investigation of Synthesized Epoxy-Polyurethane/Silica Nanocomposites

Silicon - In this research, epoxy polyurethane-nano silica nanocomposites have been synthesized using an in-situ method, for which SiO2 nanocomposites had been initially ready in N,...     

Influence of tungstate ion dopants in corrosion protection behavior of polyaniline coating on mild steel

Electropolymerization of polyaniline (PANI) and polyaniline‐tungstate (PANIW) coatings on mild steel were successfully performed using cyclic voltammetry technique. Processes were carried out in aqueous electrolyte solutions of 0.3 M oxalic acid + 0.1 M aniline and 0.3 M oxalic acid + 0.1 M aniline + 0.001 M sodium tungstate dehydrate. Corrosion protection of PANI and PANIW coatings was evaluated with the help of open circuit potential (E_ocp) monitoring and electrochemical impedance spectroscopy (EIS) methods. All the results reveal the influence of additional doping agent (i.e., tungstate) in corrosion protection behavior of PANI coating.     

Comparison between polyaniline‐phosphate and polypyrrole‐phosphate composite coatings for mild steel corrosion protection

Polyaniline, polypyrrole and their composites have been deposited on mild steel electrode from aqueous oxalic acid solution by using cyclic voltammetry (CV) technique. The resulting coatings were characterized by scanning electron microscopy and EDX analysis. The protective performance against corrosion of these coatings is evaluated by using electrochemical impedance spectroscopy (EIS) technique in corrosive solution (3.5% NaCl). Impedance data indicates a noticeable enhancement of protection against corrosion processes. Also, comparison of polyaniline‐phosphate and polypyrrole‐phosphate coatings indicates better corrosion protection with polyaniline‐phosphate coatings.     

Does Density Aggravate the COVID-19 Pandemic?

Abstract

Problem, research strategy, and findings: The impact of density on emerging highly contagious infectious diseases has rarely been studied. In theory, dense areas lead to more face-to-face interaction among residents, which makes them potential hotspots for the rapid spread of pandemics. On the other hand, dense areas may have better access to health care facilities and greater implementation of social distancing policies and practices. The current COVID-19 pandemic is a perfect case study to investigate these relationships. Our study uses structural equation modeling to account for both direct and indirect impacts of density on the COVID-19 infection and mortality rates for 913?U.S. metropolitan counties, controlling for key confounding factors. We find metropolitan population to be one of the most significant predictors of infection rates; larger metropolitan areas have higher infection and higher mortality rates. We also find that after controlling for metropolitan population, county density is not significantly related to the infection rate, possibly due to more adherence to social distancing guidelines. However, counties with higher densities have significantly lower virus-related mortality rates than do counties with lower densities, possibly due to superior health care systems.

Takeaway for practice: These findings suggest that connectivity matters more than density in the spread of the COVID-19 pandemic. Large metropolitan areas with a higher number of counties tightly linked together through economic, social, and commuting relationships are the most vulnerable to the pandemic outbreaks. They are more likely to exchange tourists and businesspeople within themselves and with other parts, thus increasing the risk of cross-border infections. Our study concludes with a key recommendation that planners continue to advocate dense development for a host of reasons, including lower death rates due to infectious diseases like COVID-19.     

Investigation on corrosion failure of Cr–Mo P11 grade pipe in primary section of a superheated steam generation system

This paper presents failure analysis of corroded steam pipes (Cr–Mo, P11 grade) at ammonia production plant. The corrosion and deposition morphologies are characterized using scanning electron microscopy. In addition, elemental composition analysis of deposited corrosion products is carried out using energy dispersive X-ray. This study clearly indicates the sensitivity of P11 grade steel pipe to intensive oxygen corrosion in steam generation systems with improper implementation of deoxygenating processes. Furthermore, this pipe grade and oxide layer on its surface are susceptible to cracking at the presence of high-level thermal stresses.     

Non‐linear behavior of yielding damped braced frames

Since the nature of an earthquake is the energy which is released due to tectonic events, improvements of behaviour of structures based on energy concepts have been a matter of great concern. Input energy must be dissipated by structures in order to decrease earthquake damage. For this purpose the YDBF (yielding damped braced frame) system is presented, which acts as a fuse when an earthquake occurs. Because of the high ductility of this system, damage to the main structural elements such as columns is prevented, and because of the non‐linear behaviour of such a system, which is based on the yielding of ductile steel, YDBF increases hysteretic dissipated energy. This class of dampers often yields in high or intermediate earthquake shakes and their hysteretic loops are relatively thick and stable. In this research seven YDBF system are modelled. These models are tested with various percentages of opening and the results of structural behaviour due to variation of opening percentages are compared. Copyright © 2004 John Wiley & Sons, Ltd.     

Buckling behavior improvement of steel plate shear wall systems

To improve buckling stability and to prevent early elastic buckling of infill plates, vertical and horizontal plate stiffeners are designed for steel plate shear wall (SPSW) systems. Furthermore, effective design of stiffeners for SPSW systems results in improved structural behavior, such as increase of stiffness, capacity and energy absorption. In this paper, the effect of stiffeners is studied on SPSW structural behavior and consequently a rational method is proposed to determine the minimum required moment of inertia for stiffeners resulting in local buckling mode of the infill plate. The proposed requirement is then compared to results obtained from tests previously conducted, as well as those gained from finite element (FE) analyses performed for this study. Copyright © 2007 John Wiley & Sons, Ltd.     

Actor-based slicing techniques for efficient reduction of Rebeca models

Slicing is a program analysis technique which can be used for reducing the size of the model and avoid state space explosion in model checking. In this work a static slicing technique is proposed for reducing Rebeca models with respect to a property. For applying the actor-based slicing techniques, the Rebeca control flow graph (RCFG) and the Rebeca dependence graph (RDG) are introduced. We propose two different approaches for constructing the RDG, where each approach can be more effective under certain conditions. As the static slicing usually produces large slices, two other slicing-based reduction techniques, step-wise slicing and bounded slicing, are proposed as simple novel ideas. Step-wise slicing first generates slices that overapproximate the behavior of the original model and then refines it, and bounded slicing is based on the semantics of nondeterministic assignments in Rebeca. We also propose a static slicing algorithm for deadlock detection (in absence of any particular property). The efficiency of these techniques is checked by applying them to several case studies which are included in this paper. Similar techniques can be applied on the other actor-based languages.